A flowchart in FIG. 23 represents a conventional method of analyzing additives included in polyolefin-group resins, such as polypropylene (referred to as PP) and polyethylene (referred to as PE). First, the additives are extracted for 8 hours with a solvent, such as chloroform, heated to its boiling point, from pellets of the polyolefin-group resin, referred to as a sample (referred to as process “A”). Here, this extraction is performed twice, and thus, all of the additives are extracted. Next, after chloroform is removed from the additives, reflux extraction is performed for 1 hour using heated acetone (referred to as process “B”); then, after the acetone is removed, an analysis is performed by either liquid chromatography or gas chromatography. Consequently, the additives, such as an antioxidant and a flame retardant, are identified and quantified. On the other hand, regarding the residues remaining after the chloroform extraction, extraction is performed for 4 hours using heated N,N-dimethylformamide (referred to as process “C”); then, the extract obtained is analyzed by infrared spectroscopy, and thus, an additive such as a metal deactivator is identified.
In the process “A”, an acetone/toluene solvent mixture, 1:1 by volume ratio, can also be used as the solvent instead of chloroform. As a method for the process “A”, for example, the Soxhlet extraction method is used, in which the extraction is not limited to two times, but performed more than twice in response to necessity. Here, in the Soxhlet extraction method used for the process “A”, because the extraction is performed with the solution being refluxed, a specified volume of the solution is needed; thus, as chloroform, for example, a volume of approximately 100 ml is needed. Therefore, the sample pellets weigh approximately 10 g. Additionally, in the process “A”, because the extraction is performed using the solvent heated close to its boiling point, due to the resin of the base material being partially extracted, there is interference in the analysis; therefore, by re-extracting the additives from chloroform extract using acetone, which can only extract the additives, there is no interference in the analysis. Here, in the process “A”, if a solvent that extracts only the additives is used, the extraction time is extended (for example, as referred to in Non-Patent Document 1).
[Non-Patent Document 1]    Technical Information Institute, Ed., “Separation and Analysis Technology of Polymer Additives”, on page 19-21.